A female-centered drama about two teens with cancer doesn't sound like your typical light, summer action fare, but "The Fault in Our Stars" still had one of the strongest openings of the year to date, earning an estimated $48.2 million this weekend.

Actually, most pundits were expecting it to do fairly well, given the popularity of both the source novel and of star Shailene Woodley. Even so, predictions were mostly in the mid-30s, at least $10 million below the film's actual performance.

What's behind the film's unexpected surge? Here are a few possibilities:

Girl Power. We saw it last week with "Maleficent." We're seeing it again this week, not just with "Fault," but also with such movies as "Belle" (the historical drama that's No. 12 this week, even though its six weeks old and is playing on just 476 screens), "The Other Woman" (still as high as No. 14 after seven weeks) and the new romantic comedy "Obvious Child" (which opened Friday and earned the weekend's top per-screen average, $27,000, compared to $15,191 for "Fault"). This season's movies that target female viewers are showing their stamina, even as the traditional male-oriented action and comedy blockbusters fizzle on entry ("Blended," "A Million Ways to Die in the West") or deflate after their first weekend ("X-Men: Days of Future Past," "Godzilla," "The Amazing Spider-Man 2").

The latest example is the new Tom Cruise vehicle, "Edge of Tomorrow," which, despite strong reviews, opened at just No. 3, with an estimated $29.1 million. That's at the low end of what was expected. Cruise's action-fests tend to do better overseas, but even this one has opened with lackluster numbers abroad. It could be that audiences are getting tired of Cruise's shtick; viewers gave it just a so-so B+ at CinemaScore. Meanwhile, "Maleficent" held up well in its second weekend, losing just 52 percent of its first-week business (a modest drop for a blockbuster) and finished second with an estimated $33.5 million. That decline was a little smaller than predicted. It seems one more sign that this summer's moviegoers would rather see what the gals have to offer than what the guys do.

Shailene Woodley. She's not quite the next J-Law yet, despite her talk-show ubiquity and her quirky personality (enough with the anecdotes about eating clay, please). But "Divergent" (which opened with $54.6 million) and now "Fault," within a few months of each other, show Woodley to be a star who can open movies to the tune of $50 million. Sure, it helped that she re-teamed with "Divergent" co-star Ansel Elgort in "Fault," and the movie had a lot of other things going for it (see below), but Woodley will get most of the credit. Certainly, it's hard to imagine another actress her age (22) with the poise to pull off this difficult tragic, romantic role.

Smart Marketing. The movie did a good job using social media to reach its intended young-adult audience and cultivate readers of John Green's bestseller. The effort culminated in a special screening Thursday night that included a simulcast Q&A session with the cast, filmmakers, and Green. In fact, the movie did so well Thursday night that it overinflated expectations, with some pundits taking back their initial projections and declaring that the movie would enjoy a $60 million debut. As it turned out, the film did most of its business on Friday, with fall-off over the rest of the weekend, but again, remember that this is a drama about teens with cancer that opened with nearly $50 million at the beginning of June. That just doesn't happen without a well-targeted marketing campaign.

Execution. Of course, all that marketing wouldn't have mattered if the movie didn't work; word-of-mouth from the disappointed fanbase would have killed it before breakfast on Friday. But viewers gave it an A at CinemaScore, so they must have felt it delivered. It didn't hurt that Green was kept in the loop during production even though he didn't write the screenplay (the guys who did, Scott Neustadter and Michael H. Weber, also wrote Woodley's acclaimed indie romance hit from last summer, "The Spectacular Now"), or that director Josh Boone avoided the missteps that could have left the film mired in sentimentality.

Timing. It also didn't hurt that the movie faced weak competition at the box office. Yeah, that's right, Tom Cruise, we're talking about you. Really, "Fault" would have been smart counter-programming just about any weekend in June, since there's precious little other female-centered fare opening this month. Last week, it might have been clobbered by "Maleficent." This week, however, "Maleficent" just looks like "Fault"'s opening act, a film meant to whet your appetite and to get you thinking about tragic romance and female empowerment. Plus, by opening this early, the film has all of June, and maybe all of summer, to keep proving that what we think we know about what comprises a summer smash is wrong.

If watching Bette Midler bond with pal Barbara Hershey's little girl as Hershey wastes elegantly away from an incurable disease doesn't get you, then Midler slamming it home with her rendition of "Wind Beneath My Wings" will bludgeon you into blubbering submission.